Hurricane IGOR (Text)

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HURRICANE IGOR DISCUSSION NUMBER 47
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST SUN SEP 19 2010
THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS MEASURED PEAK
FLIGHT-LEVEL AND SFMR WINDS OF 82 KT AND 68 KT...RESPECTIVELY.
BASED ON THESE DATA...THE INITIAL INTENSITY IS LOWERED SLIGHTLY
TO 70 KT. THE WIND FIELD REMAINS QUITE LARGE AND SOME OF THE WIND
RADII HAVE BEEN EXPENDED OUTWARD BASED ON THE AIRCRAFT AND EARLIER
ASCAT DATA. LITTLE CHANGE IN INTENSITY IS EXPECTED WHILE IGOR
REMAINS A TROPICAL CYCLONE. THE GLOBAL MODELS INDICATE THAT
EXTRATROPICAL TRANSITION SHOULD BEGIN ON MONDAY...AND BE
COMPLETED IN ABOUT 48 HOURS. GRADUAL WEAKENING IS SHOWN BY THE
DYNAMICAL MODELS AFTER IGOR BECOMES EXTRATROPICAL...AND THIS IS
REFLECTED IN THE OFFICIAL FORECAST.
THE AIRCRAFT FIXES WERE A FEW TENTHS OF A DEGREE WEST OF THE EARLIER
SATELLITE ESTIMATES. THIS HAS REQUIRED A LITTLE ADJUSTMENT TO THE
INITIAL POSITION AND MOTION. THE UPDATED POSITION HAS ALSO REQUIRED
A SMALL WESTWARD SHIFT IN THE EARLY PORTION OF THE FORECAST TRACK.
THERE HAVE BEEN NO CHANGES TO THE TRACK FORECAST PHILOSOPHY...
HOWEVER...AND IGOR IS EXPECTED TO TURN NORTHEAST TONIGHT AHEAD OF A
MID-LATITUDE TROUGH MOVING OFF THE COAST OF NORTH AMERICA. THE
GLOBAL MODELS HAVE BEEN VERY INCONSISTENT IN THE EXTRATROPICAL
PORTION OF THE TRACK AND THERE REMAINS A VERY LARGE SPREAD IN THE
GUIDANCE AT 3 TO 5 DAYS. THE OFFICIAL FORECAST HAS BEEN ADJUSTED A
LITTLE EASTWARD AT 72 HOURS AND BEYOND...TO BE IN BETTER AGREEMENT
WITH THE MULTI-MODEL CONSENSUS.
ALTHOUGH THE CENTER OF IGOR IS LIKELY TO PASS WEST OF
BERMUDA...HURRICANE FORCE WINDS EXTEND A LARGE DISTANCE FROM THE
CENTER AND SIGNIFICANT IMPACTS ARE BEING FELT ON THE ISLAND.
FORECAST POSITIONS AND MAX WINDS
INITIAL 19/2100Z 31.5N 65.9W 70 KT
12HR VT 20/0600Z 33.6N 65.3W 70 KT
24HR VT 20/1800Z 36.9N 62.8W 70 KT
36HR VT 21/0600Z 40.6N 58.1W 70 KT
48HR VT 21/1800Z 45.0N 52.0W 65 KT...POST-TROP/EXTRATROP
72HR VT 22/1800Z 51.0N 41.0W 55 KT...POST-TROP/EXTRATROP
96HR VT 23/1800Z 55.0N 37.5W 50 KT...POST-TROP/EXTRATROP
120HR VT 24/1800Z 60.0N 37.5W 45 KT...POST-TROP/EXTRATROP
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FORECASTER BROWN
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